The present invention relates to thermosensitive, thermo-reversible pharmaceutical compositions. In particular, the present invention relates to sustained release, gelable (thermosensitive) botulinum toxin pharmaceutical compositions formulated with a poloxamer.
A pharmaceutical composition is a formulation which contains at least one active ingredient (such as a botulinum toxin) as well as, for example, one or more excipients, buffers, carriers, stabilizers, preservatives and/or bulking agents, and is suitable for administration to a patient to achieve a desired diagnostic result or therapeutic effect. The pharmaceutical compositions disclosed herein have diagnostic, therapeutic, cosmetic and/or research utility.
For storage stability and convenience of handling, a pharmaceutical composition can be formulated as a lyophilized (i.e. freeze dried) or vacuum dried powder which can be reconstituted with a suitable fluid, such as saline or water, prior to administration to a patient. Alternately, the pharmaceutical composition can be formulated as a ready to use aqueous solution or suspension. A pharmaceutical composition can contain a proteinaceous active ingredient. Unfortunately, a protein active ingredient can be very difficult to stabilize (i.e. maintained in a state where loss of biological activity is minimized), resulting therefore in a loss of protein and/or loss of protein activity during the formulation, reconstitution (if required) and during the period of storage prior to use of a protein containing pharmaceutical composition. Stability problems can occur because of protein denaturation, degradation, dimerization, and/or polymerization. Various excipients, such as albumin and gelatin have been used with differing degrees of success to try and stabilize a protein active ingredient present in a pharmaceutical composition. Additionally, cryoprotectants such as alcohols have been used to reduce protein denaturation under the freezing conditions of lyophilization.
Thermosensitive pharmaceutical compositions, which form in-situ gels, are known. See eg U.S. Pat. No. 5,278,201. Poloxamers are nontoxic block copolymers of poly(ethylene oxide), poly(propylene oxide) and poly(ethylene oxide) (PEO-PPO-PEO). Certain poloxamers exhibit reversible thermal gelation. Thus a solution of a protein and a poloxamer prepared at low temperatures and injected will form a gel as it warms to body temperature. Subsequently the protein is slowly released from the gel. A gelable, thermo-reversible formulation comprising poloxamer 407 at a 22 wt % concentration has been prepared with the model protein drugs α-chymotrypsin and lactate dehydrogenase. Stratton L., et al., Drug delivery matrix containing native protein precipitates suspended in a poloxamer gel, J Pharm Sci 86(9); 1006-1010, September 1996. Formulations of certain adhesive proteins and poloxamer 127 have been made. Huang K., et al., Synthesis and characterization of self assembling block copolymers containing adhesive moieties, Polymer Preprints 2001, 42(2), 147-148. Additionally, poloxamer 188 and poloxamer 407 have been used an excipients in protein drug pharmaceutical compositions. Jeong B., et al., Thermosensitive sol-gel reversible hydrogels, Adv Drug Del Rev, 54(1); 37-51, Jan. 17, 2002. Published patent application WO 2007/041664 discloses use a pharmaceutical composition comprising a botulinum toxin and a poloxamer 188.
Botulinum toxins have been used for various therapeutic and cosmetic purposes including treating cervical dystonia, blepharospasm, strabismus, spasticity, headache, hyperhidrosis, overactive bladder, rhinitis, bruxism, enlarged prostate, achalasia, anismus, sphincter of Oddi malfunction, acne, tremors, juvenile cerebral palsy, and facial wrinkles.
Commercially available botulinum toxin containing pharmaceutical compositions include BOTOX® (Botulinum toxin type A neurotoxin complex with human serum albumin and sodium chloride) available from Allergan, Inc., of Irvine, Calif. in 100 unit vials as a lyophilized powder to be reconstituted with 0.9% sodium chloride before use), DYSPORT® (Clostridium botulinum type A toxin haemagglutinin complex with human serum albumin and lactose in the formulation), available from Ipsen Limited, Berkshire, U.K. as a powder to be reconstituted with 0.9% sodium chloride before use), and MYOBLOC™ (an injectable solution comprising botulinum toxin type B, human serum albumin, sodium succinate, and sodium chloride at about pH 5.6, available from Solstice Neurosciences, Inc., South San Francisco, Calif.).
Botulinum toxin is a large protein for incorporation into a pharmaceutical formulation (the molecular weight of the botulinum toxin type A complex is 900 kD) and is inherently fragile and labile. The size of the toxin complex makes it much more friable and labile than smaller, less complex proteins, thereby compounding the formulation and handling difficulties if botulinum toxin stability is to be maintained. Hence, a botulinum toxin stabilizer must be able to interact with the toxin in a manner which does not denature, fragment or otherwise detoxify the toxin molecule or cause disassociation of the non-toxin proteins present in the toxin complex.
As the most lethal known biological product, exceptional safety, precision, and accuracy are called for at all steps of the formulation of a botulinum toxin containing pharmaceutical composition. Thus, a botulinum toxin stabilizer should not itself be toxic or difficult to handle so as to not exacerbate the already extremely stringent botulinum toxin containing pharmaceutical composition formulation requirements.
Since botulinum toxin was the first microbial toxin to be approved (by the U.S. Food and Drug Administration in 1989) for injection for the treatment of human disease, specific protocols had to be developed and approved for the culturing, bulk production, formulation into a pharmaceutical and use of botulinum toxin. Important considerations are toxin purity and dose for injection. The production by culturing and the purification must be carried out so that the toxin is not exposed to any substance that might contaminate the final product in even trace amounts and cause undue reactions in the patient. These restrictions require culturing in simplified medium without the use of animal meat products and purification by procedures not involving synthetic solvents or resins. Preparation of toxin using enzymes, various exchangers, such as those present in chromatography columns and synthetic solvents, can introduce contaminants and are therefore excluded from preferred formulation steps. Furthermore, botulinum toxin type A is readily denatured at temperatures above 40 degrees Centigrade, loses toxicity when bubbles form at the air/liquid interface and denatures in the presence of nitrogen or carbon dioxide.
Particular difficulties exist to stabilize botulinum toxin type A, because type A consists of a toxin molecule of about 150 kD in noncovalent association with nontoxin proteins weighing about 750 kD. The nontoxin proteins are believed to preserve or help stabilize the secondary and tertiary structures upon which toxicity is dependant. Procedures or protocols applicable to the stabilization of nonproteins or to relatively smaller proteins are not applicable to the problems inherent with stabilization of the botulinum toxin complexes, such as the 900 kD botulinum toxin type A complex. Thus while from pH 3.5 to 6.8 the type A toxin and non toxin proteins are bound together noncovalently, under slightly alkaline conditions (pH>7.1) the very labile about 150 kD neurotoxic component of a botulinum toxin is released from the botulinum toxin complex. Xeomin™ is the trade name for a neurotoxic component botulinum toxin type A pharmaceutical composition available from Merz Pharmaceuticals (Frankfurt, Germany).
In some instances botulinum toxins, when used as therapeutic drugs, are known to migrate from the site of injection at various rates and distances, sometimes resulting in loss of effect at the desired muscle.
Solid botulinum toxin implants are known. See e.g., U.S. Pat. Nos. 6,306,423; 6,312,708, for a discussion of exemplary solid implants and applications. Additionally formulation of a botulinum toxin in a viscous carrier such as a hyaluronic acid is known; U.S. applications Ser. Nos. 11/954,629, and 11/954,602, filed Dec. 12, 2007.
What is needed is a biocompatible, gelable (thermoplastic) pharmaceutical composition comprising a stabilized botulinum toxin so that the composition can be administered as a liquid yet forms a sustained release gel upon administration; thereby localizing the effect and controlling release of the toxin to enhance the effect per dose.